Re: [Discuss-gnuradio] Expected behavior during underruns

[Josh Blum]

On 12/09/2010 02:11 AM, Patrik Eliardsson wrote:
> Dear list,
> 
> What is the expected behavior when we get underruns with the UHD and the flow 
> control using the USRP2?
> 

The host will get an async packet marked underflow and print a U. You
can get the timestamp of this packet through the recv_async_msg interface.

The USRP2 will continue to send subsequent packets ASAP until the burst
has ended. It is possible to configure the device to discard all packets
until a new burst begins.

When underflowing, there are no random samples, the TX state machine
goes into an IDLE mode. The effect of this depends on the daughterboard.
But its basically turning the transmitter off.

-JOsh

> 1) When we get underruns, does the usrp2 send some random samples until the 
> host computer manage to feed the usrp2 and then starts to consume the 'old' 
> samples from the host computer?
> 
> Or
> 
> 2) When we get underruns, does the usrp2 send some random samples while 
> throwing away old samples until the host computer manage to feed the usrp2 
> with samples to be sent in the future? 
> 
> Or does it work in another way?
> 
> Br,
> Patrik
> 
> 
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